The purpose of the study is the investigation of the mechanisms in the brain which integrate neural and hormonal systems in the regulation of the internal body temperature, the cardiovascular system, metabolism, and reproduction. We have chosen to study the baboon because this infrahuman primate is phylogenetically close to the human, and information obtained should have relevance to human physiology. Local cooling and warming is performed in the base of the brain of conscious baboons via surgically implanted thermodes. In other experiments, baboons are placed in a cold (6 degrees centigrade) environment for 3 days to 13 weeks. The resulting mobilization of heat-producing and heat-conserving activities, such as shivering, vasoconstriction, increased metabolic rate, secretion of metabolic hormones, and behavioral responses, is studied in detail. By correlating alterations in these various parameters, an attempt is made to provide a synthesis of the coordinated responses. The neurochemical mechanisms within the hypothalamus at the base of the brain which mediate the secretion of hormones from the anterior pituitary are studied by microinjection of putative neurotransmitters into descrete regions. Fully conscious baboons loosely restrained in primate chairs are studied in these experiments. Blood samples drawn from chronic catheters in veins and arteries are analyzed for hormonal and substrate (fuel) changes. Thus, the regulation of the hormones concerned with ovulation (LH) and lactation (prolactin) as well as with thermoregulation (TSH, ACTH, growth hormone) may be studied.